In a thick and tall heavy skillet or casserole dish, heat the oil over medium-high heat. Once hot, add the chicken pieces. Brown on one side, for about 4 to 5 minutes and then flip and brown on the other side, for another 3 to 4 minutes. Don't try to flip too soon or the skin will stick to the skillet. Remove the chicken pieces and place in a bowl. You may remove the skin if you wish, I don't.

Add the onion to the skillet and cook, stirring for about 3 to 4 minutes, until softened. Add the garlic and saute until fragrant, for about 20 seconds. Make room in the pan and add the tomatillos. Let it cook all together, for about 6 to 8 minutes. Add the piloncillo, the chipotles and their sauce and stir well. Once it comes to a simmer incorporate the chicken pieces along with the chicken broth and cook for about 30 to 35 minutes, stirring occasionally. The sauce should be chunky and thick, and the chicken fully cooked.